The present invention relates to a substrate heater for heating a semiconductor wafer, a liquid crystal substrate, and the like, which is used in a semiconductor fabricating process. More specifically, the present invention relates to a substrate heater where a resistance-heating element is embedded in a ceramic base.
Semiconductor equipment employs a substrate heater. The substrate heater employs a ceramic heater where a linear resistance-heating element is embedded in a discoid ceramic base. The substrate heater also extensively employs a ceramic heater with an electrostatic chuck function, where an electrostatic chuck electrode for fixing a substrate by adsorption is embedded with a resistance-heating element.
This ceramic heater includes a base formed of highly corrosion resistant ceramic, and the resistance-heating element is not exposed to the outside. For this reason, the ceramic heater is suitable for use in a chemical vapor deposition (CVD) apparatus, a dry etching apparatus, and the like, which frequently apply corrosive gas.
The ceramic heater employed in the semiconductor equipment is applicable to a wide temperature range depending on the application, specifically a range of room temperature to a high temperature equal to or above 500° C. Meanwhile, for improvement in product yields, it is important to ensure temperature uniformity on the substrate. For this reason, the substrate heater is required to have temperature uniformity at a high temperature on a substrate-placing surface, that is, a substrate heating surface.
For example, to improve temperature uniformity on a heating surface of a ceramic heater, conventionally, a method of achieving temperature uniformity on a heating surface has been disclosed (see Japanese Patent Publication No. 2527836, FIG. 1 and FIG. 3, etc.). According to this method, the spiral resistance-heating element embedded in the ceramic base is adjusted in spiral pitch and shape depending on the location.
In a substrate heater used in a CVD apparatus or a dry etching apparatus, the resistance-heating element has a terminal drawn outside without being exposed to the corrosive gas. For this reason, the following structure is frequently adopted, where the lower central portion of the ceramic base is joined to a shaft as a tubular member, and the shaft houses the terminal of the resistance-heating element, a feed bar to be connected thereto, and the like therein.